The Tottenham boss was delighted for his fellowScot after Wednesday night's 1-1 draw with Bayern Munich secured United's place in the quarter-finals of the Champions' League.
"If he wins the European Cup he will go down as one of the great managers - and justifiably so," Graham said, "because he has taken a club which had not won the championship for 26 years and won it many times.
"You can only look at the man's record and say that if he wins the European Cup he will be up there with Busby, Shankly and Stein."
It is Graham's job to try to bring Ferguson back down to earth today when United visit White Hart Lane in the Premiership.
Spurs dumped United out of the English League Cup this month with a 3-1 victory and Graham was given a timely boost on the eve of today's clash when David Ginola pledged his future to the club.
Ginola was widely expected to the first big-name casualty when Graham took over as manager after the departure of Christian Gross.
But he has flourished in recent weeks, producing a string of top-class performances.
Ginola said: "I want to feel at home here - to stay and help Tottenham to the top of the league."
Meanwhile, United have admitted they have no timetable in place for new contract talks with manager Ferguson, who last month celebrated 12 years at the club.
